[LLVMdev] -gcolumn-info and PR 14106

Alexey Samsonov vonosmas at gmail.com
Wed Jul 2 08:46:15 PDT 2014


On Wed, Jul 2, 2014 at 8:37 AM, Diego Novillo <dnovillo at google.com> wrote:

> On Tue, Jul 1, 2014 at 7:56 PM, Alexey Samsonov <vonosmas at gmail.com>
> wrote:
> >
> > On Thu, Jun 26, 2014 at 9:46 AM, Diego Novillo <dnovillo at google.com>
> wrote:
> >>
> >> For -Rpass, and other related uses, I am looking at enabling column info
> >> by default. David pointed me at PR 14106, which seems to be the original
> >> motivation for introducing -gcolumn-info. However, I am finding no
> >> differences when using it on this test.  I've tried building
> with/without
> >> -gcolumn-info and found almost no difference in compile time (+0.4%):
> >>
> >> $ /usr/bin/time clang -w -fno-builtin -O2 -g -gcolumn-info
> test-tgmath2.i
> >> 474.38user 2.10system 7:58.00elapsed 99%CPU
> >>
> >> $ /usr/bin/time clang -w -fno-builtin -O2 -g  test-tgmath2.i
> >> 472.63user 2.02system 7:56.11elapsed 99%CPU
> >>
> >> I'm running clang from trunk @211693.
> >>
> >> The size of all debug sections (according to readelf) are:
> >>
> >> - with -g -gcolumn-info: 836,177 bytes
> >> - with -g: 826,552 bytes
> >>
> >> That's a growth of about 1% in debug info size.
> >
> >
> > What about the difference between -gmlt and -gmlt + -gcolumn-info?
>
> Debug info growth is larger in proportion (3%). Total binary size is
> roughly the same (~1%). Compile times are identical (7m47s for both).
>
> - with -gmlt -gcolumn-info: 319,792 bytes
> - with -gmlt: 310,243 bytes
>

Looks good. I think we can live with that increase. I'm certainly not
opposed
to enabling -gcolumn-info by default. For example, adding it will
automatically
give us column numbers in stack traces in sanitizer error reports.



>
>
> Diego.
>



-- 
Alexey Samsonov
vonosmas at gmail.com
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